Dependency on some operating parameters during wet oxidation of phenol by hydrogen peroxide with Fe-ZSM-5 zeolite

Wastewater originating in the chemical process industries contain high concentrations of organics that must be treated before discharge. Phenol is one of the most important of these pollutants because it is toxic, even at low concentrations. Recently, hydrogen peroxide treatment has emerged as a viable alternative oxidation technique for treatment. It does not form any harmful or intrusive by-products and it is an ecologically dean and non-toxic chemical; However, the methods for treatment of wastewater with hydrogen peroxide are based mostly on homogeneous catalysis by metal ions inducing additional pollution. From this,it was anticipated that the use of heterogeneous catalysis would be a good alternative thus opening up a new field of investigation. Previous studies, based on screening tests, evidenced the catalytic activity of an MFI zeolite Fe-ZSM-5 for phenol elimination by H(2)O(2). The oxidation tests are carried out in a batch mode, using a stirred glass reader. The influence of pH, temperature and H(2)O(2) stoichiometric ratio on the phenol oxidation rate with Fe-ZSM-5 is studied. The temperature is below 100 degrees C in order to avoid pressurization of the treatment reactor. Using a H(2)O(2) stoichiometric ratio equal to 1.5 avoids accumulation of any quinone-like by-products;Under these conditions, the catalytic system H(2)O(2)/Fe-ZSM-5 allows a total elimination of phenol and a significant TOC removal (50%) without leaching-off more than 1 ppm of Fe (III) ions. At the end of the reaction period, only carboxylic adds (maleic, fumaric, oxalic, acetic, accumulate. These latter should not be considered as a drawback of this process. The chemical oxidation process would be used only as a detoxification step and such compounds could be treated with a biological process, in a second step.